The present invention is directed to an aluminum electrolytic capacitor.
Conventional aluminum electrolytic capacitor has a structure wherein an anode foil and a cathode foil are wound together or laminated by way of a separator such as an insulating paper to form a capacitor element, wherein the anode foil has an etching foil consisting of a valve action metal such as aluminum and has a chemical film formed on the etching foil, and wherein the cathode foil consists of an etching foil made of a valve action metal such as aluminum. The capacitor element is impregnated with driving electrolyte, and is then housed into a metal case having a bottomed tubular shape, wherein the aperture of the metal case is sealed with a sealing member, and thereby an electrolytic capacitor is configured.
With respect to these types of electrolytic capacitors, a suggested conventional method for fixing a capacitor element within a metal case is that a fixing agent such as a thermoplastic resin and an epoxy resin is filled within a metal case such that a capacitor element is fixed within the metal case.
Further, as shown in FIG. 7, the Patent Document 1 (Japanese Laid-open Patent Publication No. 2000-30981) discloses an invention wherein a side surface of a metal case 2 is caulked to form a convex portion 6; and by means of the convex portion 6, a capacitor element 1 is pressed at the outer circumference surface of the capacitor element 1 such that the capacitor element 1 is fixed within the metal case 2 (Patent Document 1).
Meanwhile, in recent years, an electrolytic capacitor tends to be for use in cars. When used in cars, the capacitor sustains continuous violent vibration. The vibration stress applied to the electrolytic capacitor is greater than several tens G, and is required to have a vibration resistance of 10^6 to 10^8 times or greater, which is the fatigue limit of general metals. Hence, firm fixation of a capacitor element within a metal case is necessary.
In case of conventional fixation of a capacitor element using fixation agent, firm fixation of a capacitor element requires greater amount of fixation agent to be filled within a metal case, leading to smaller space within the metal case, which is an admissible space for increased internal pressure during use of an electrolytic capacitor. Hence, a safety device such as a pressure valve is more likely to operate, resulting in shorter lifetime of the electrolytic capacitor, which is problematic.
Further, as shown in FIG. 7, when the side surface of the metal case 3 is caulked to fix the capacitor element 1, firm fixation of the capacitor element 1 requires greater suppress strength against the capacitor element 1 achieved by providing a larger convex portion 6 which is formed when the side surface of the metal case 3 is caulked. Mechanical stress is applied to the electrode foil that forms the capacitor element 1, resulting in adverse effects to some electric properties such as leakage of current.
The present invention is proposed to solve the aforementioned problems of the conventional techniques, and it is thus an object of the present invention, among others, to provide with an electrolytic capacitor that allows for firm fixation of a capacitor element within a metal case without giving any adverse effects to the electric properties of the electrolytic capacitor.